1. Field of the Invention
(1) The present invention relates to a membrane switch having a so-called three-layered structure consisting of an upper membrane sheet, a lower membrane sheet and a spacer layer formed between both sheets, and more particularly to a membrane switch which can prevent plastic deformation of the upper membrane sheet which is pushed at the time of performing switching and can maintain a resilient restoring force for a long period, a key switch using such a membrane switch, a key board having such key switches, and a personal computer having the keyboard.
(2) Further, the present invention relates to a membrane switch which ensures stable pushing of an upper membrane sheet at the time of performing switching thus providing a stable switching operation, a key switch using such a membrane switch, a key board having such key switches, and a personal computer having the keyboard.
(3) Further, the present invention relates to a membrane switch which is capable of surely fixing a membrane sheet by adhesion to an adhesive surface of a support plate always in a flat posture without leaving bubbles between a lower surface of the lower membrane sheet of membrane switch and the adhesive surface of the support plate at the time of fixing the lower membrane sheet to the support plate, a key switch using such a membrane switch, a key board having such key switches, and a personal computer having the keyboard.
(4) Still further, the present invention relates to a key switch which guides the vertical movement of a key top by way of a pair of link members, and more particularly to a key switch which is configured to bias a key top upwardly by way of a spring member formed of a metal thin resilient plate, a key board having such key switches, and a personal computer having the keyboard.
2. Description of Related Art
(1) Conventionally, there have been proposed various membrane switches each having a three-layered structure which is comprised of a lower membrane sheet forming a lower electrode on an upper surface thereof, an upper membrane sheet forming an upper electrode on a lower surface thereof corresponding to the lower electrode, and a spacer sheet interposed between both upper and lower membrane sheets and served for making the lower electrode and the upper electrode spaced apart from each other through a switching hole formed therein corresponding to the lower electrode and the upper electrode.
In this type of membrane switch, to perform a switching operation, the upper electrode portion of the upper membrane sheet is pushed down from above using a finger directly or indirectly by way of a rubber spring, a key top or the like. Due to this switching operation, the upper electrode formed on the lower surface of the upper membrane sheet is brought into contact with the lower electrode formed on the upper surface of the lower membrane sheet through the switching hole formed in the spacer sheet so that a given switching operation is performed.
Here, there may be a case that a situation in which goods are placed on the membrane switch or a situation in which a lid cover is mounted on the membrane switch while placing goods on the membrane switch is left as it is for a long time.
In such a case, the upper membrane sheet is constituted of a resin film made of polyethylene terephthalate or the like in general and hence, the upper membrane sheet is deformed by pushing with an extremely small load. Accordingly, when the goods are placed on the membrane switch, a switch portion which corresponds to the upper electrode of the upper membrane sheet is pushed by way of the goods. As a result, a state that the upper electrode of the upper membrane sheet and the lower electrode of the lower membrane sheet are brought into contact with each other, that is, a state that the switch is turned on is continued for a long period. Here, the switching portion corresponding to the upper electrode of the upper membrane sheet is in a state that the switch portion is pushed downwardly and deformed and hence, such deformed state by pushing is held for a long period.
When the deformed state of the switch portion by pushing in the upper membrane sheet is left as it is for a long period, the switch portion is subjected to the plastic deformation and maintains the deformed state by pushing and it is no more possible to restore the original state. In such a case, the upper electrode of the upper membrane sheet and the lower electrode of the lower membrane sheet assume a switch-on state in which they are always in contact with each other and hence, there arises a drawback that the membrane switch no more performs a switching function.
The present invention has been made to solve the above-mentioned drawback of the prior art and it is an object of the present invention to provide a membrane switch which can prevent the plastic deformation of an upper membrane sheet which is pushed at the time of performing switching thereby enabling the holding of the resilient restoring force for a long period, a key switch using such a membrane switch, a keyboard having the key switches, and a personal computer having the keyboard.
(2) Further, the membrane switch has a flat laminate sheet structure, wherein the upper membrane sheet is also formed flat in general. In such a membrane switch, when the upper membrane sheet is pushed directly using a finger, although a pushing portion is formed on an upper surface of the upper membrane sheet by printing or the like for facilitating finding of the pushing portion with eyes, it is not always possible to push an appropriate position of the pushing portion with the finger and hence, it is difficult to perform a stable switching operation.
Further, when the flat upper membrane sheet is indirectly pushed by way of a so-called rubber spring or a key top which is generally known, there exist the irregularities in the accuracy of size attributed to manufacturing thereof and such irregularities in the accuracy of size directly affects influences on the pushing characteristics of the membrane switch. Accordingly, although it is possible to push the appropriate position of the pushing portion of the upper sheet by way of the rubber spring or the key top so long as the accuracy in size of the rubber spring or the key top falls within proper range, when the accuracy in size does not fall within proper range, there may be a case that the upper sheet is pushed in a state that the rubber spring or the key top is inclined. In such a case, it is difficult to perform the stable switching operation in the manner as the above-mentioned case.
The present invention has been made to solve the above-mentioned drawback of the prior art and it is an object of the present invention to provide a membrane switch which can push the upper membrane sheet in a stable manner at the time of performing switching thereby ensuring the stable switching operation, a key switch using such a membrane switch, a keyboard having the key switches, and a personal computer having the keyboard.
(3) Further, the lower membrane sheet, the spacer sheet and the upper membrane sheet which constitute the membrane switch are formed of a polyethylene terephthalate film in general and their thickness is small. Accordingly, the membrane switch per se has large resiliency and hence, handling of the membrane switch is cumbersome and difficult in many case.
It is not often that such a membrane switch is used in a single form and the membrane switch is generally used in a state that the membrane switch is mounted on a support plate or the like. In many cases, the membrane switch is fixed by adhesion to the support plate or the like using an adhesive agent or a pressure sensitive adhesive double coated tape. To fix the membrane switch to the support plate or the like by adhesion, an adhesive agent is applied to the lower surface of the lower membrane sheet or a pressure sensitive adhesive double coated tape is laminated to the lower surface of the lower membrane sheet and then the lower membrane sheet is fixed by adhesion to the support plate or the like.
However, since the membrane switch has the large resiliency as mentioned previously, it is difficult to handle the membrane switch in a flat state. Accordingly, in fixing the membrane switch to the support plate or the like by adhesion, there exists a considerable fear that bubbles remain between the lower membrane sheet and the support plate or the like.
When the bubbles remain between the lower membrane sheet and an adhering surface of the support plate or the like, irregularities are formed on a surface of the membrane switch thus giving rise to an unstable switching operation.
Further, when bubbles remain below the lower membrane sheet corresponding to the switching hole formed in the spacer sheet, there may arise a state in which the upper electrode of the upper membrane sheet and the lower electrode of the lower membrane sheet are brought into contact with each other. In such a case, a switch-on state is continued and hence, the membrane switch can no more perform its function as a switch.
The present invention has been made to solve the above-mentioned drawback of the prior art and it is an object of the present invention to provide a membrane switch which can surely fix the membrane sheet by adhesion to the adhering surface of the support plate while always holding the membrane sheet in a flat state without leaving bubbles between the lower surface of the lower membrane sheet and the adhering surface of the support plate at the time of fixing the lower membrane sheet of the membrane switch by adhesion to the support plate or the like, a key switch using such a membrane switch, a keyboard having the key switches, and a personal computer having the keyboard.
(4) Further, conventionally, there have been proposed various types of key switches which are attached to a keyboard of a notebook type personal computer and are configured such that the vertical movement of each key top is guided by a pair of link members.
For example, Japanese Laid-open Patent Publication 172380/1998 discloses a key switch in which the vertical movement of a key top is guided by way of a pair of links having gears which are movably engaged with a lower surface of the key top on which a pushdown projection is formed and an upper surface of a base mold, and a rubber sheet formed of silicon rubber or the like is extended in a suspended manner between projections for suspending rubber sheet which are formed on respective links having gears.
In the above-mentioned key switch, in a state that the key top is not pushed down, the pushdown projection which is brought into contact with the rubber sheet is biased upwardly due to a resilient force of the rubber sheet so as to hold the key top in the non-pushdown state. When the switching operation is performed, along with the pushing down of the key top, the rubber sheet is pushed down by way of the pushdown projection so that, due to the pushdown projection, switching is performed by a switching portion of the membrane sheet which is disposed below the base mold along with the rubber sheet.
However, in the key switch described in the above-mentioned Japanese Laid-open Patent Publication 172380/1998, the rubber sheet is used as a spring member to bias the key top upwardly. This rubber sheet is liable to easily receive the influence attributed to the use environment such as temperature, humidity or the like and hence, the rubber sheet is degraded in a relatively short period and exhibits poor durability. Further, to hold the key top at the non-pushdown position, as shown in FIG. 2 of Japanese Laid-open Patent Publication 172380/1998, it is necessary to bias the key top upwardly using the resilient force of the rubber sheet by always bringing the pushdown projection of the key top into contact with an upper surface of the rubber sheet. In such a situation, the rubber sheet is always subjected to the elastic deformation. When the rubber sheet is always held in such an elastically deformed state, along with the fact that the rubber sheet exhibits poor durability, the rubber sheet is subjected to a permanent deformation and does not return to the original state (state in which the rubber sheet has an original elastic force). Accordingly, the elastic force of the rubber sheet is gradually decreased and hence, the non-pushdown position of the key top is also gradually moved to a downward position. As a result, there is a possibility that the characteristics of the key top such as the operability of the key or the like are changed.
In performing the switching operation with the switching portion of the membrane sheet disposed below the base mold, the constitution which pushes the switch portion together with the rubber sheet by way of the pushdown projection which is formed on the lower surface of the key top is adopted. To achieve such a constitution, as shown in FIG. 1 and FIG. 2 of Japanese Laid-open Patent Publication 172380/1998, it is necessary to set the length of the pushdown projection to a length approximately three times as large as a thickness of the key top such that the pushdown projection projects sufficiently downwardly from a lower end of the key top. Accordingly, the height of the key top at the non-pushdown position becomes inevitably large and hence, it is extremely difficult to reduce the thickness of the key switch.
The present invention has been made to solve the above-mentioned drawback of the prior art and it is an object of the present invention to provide a key switch which can ensure the stable characteristics such as key operability for a long period without receiving influence attributed to the use environment and, at the same time, can easily reduce the thickness thereof by using a spring member formed of a metal thin resilient plate in guiding the vertical movement of a key top, a keyboard having the key switch, and a personal computer having the keyboard.
(1) To accomplish the above purposes, according to one aspect of the present invention, there is provided a membrane switch which comprises a lower membrane sheet which forms a lower electrode on an upper surface thereof, an upper membrane sheet which forms an upper electrode on a lower surface thereof corresponding to the lower electrode, and a spacer layer which is provided between the lower membrane sheet and the upper membrane sheet and in which a switching hole is formed corresponding to the lower electrode and the upper electrode, and makes the lower electrode and the upper electrode spaced apart from each other by way of the switching hole, wherein a spring sheet formed of a thin metal plate is arranged over the upper membrane sheet.
In the above-mentioned membrane switch, since the spring sheet formed of the thin metal plate is arranged over the upper membrane sheet, even when a state in which goods are placed on the upper membrane sheet is held for a long period, the upper membrane sheet is not plastically deformed due to a large resilient force of the spring sheet so that it is possible to perform the reliable switching operation while holding a resilient restoring force over a long period.
Here, the above-mentioned spacer layer may be formed between the upper membrane sheet and the lower membrane sheet, and may be constituted of an adhesive agent layer which adheres both membrane sheets in a laminated manner or is constituted of a spacer sheet which is formed of a sheet equal to the upper membrane sheet and the lower membrane sheet.
Further, it is preferable that a pair of slits are formed in the spring sheet corresponding to both sides of the upper electrode of the upper membrane sheet. In such a membrane switch, since a pair of slits are formed corresponding to both sides of the upper electrode of the upper membrane sheet, even when a pushdown load is applied to a switching portion of the spring sheet corresponding to the upper electrode by way of a finger, a rubber spring, a key top or the like, it is possible to concentrate the pushdown load to the switch portion by preventing the pushdown load from being dispersed over the whole spring sheet. Accordingly, it is possible to rapidly perform the switching operation by bringing the upper electrode of the upper membrane sheet and the lower electrode of the lower membrane sheet into contact with each other with a small pushdown load.
Further, according to another aspect of the present invention, there is provided key switches each of which comprises a key top which forms a pushdown projection on a lower surface thereof, a holder member which is arranged below the key top and forms an opening therein corresponding to the pushdown projection, a first link member and a second link member which are movably connected to and engaged with a lower surface of the key top and the holder member and guide the vertical movement of the key top, a spring member which biases the key top upwardly, and a membrane switch including a lower membrane sheet which is arranged below the holder member and forms a lower electrode on an upper surface thereof corresponding to the opening, an upper membrane sheet which forms an upper electrode on a lower surface thereof corresponding to the lower electrode, and a spacer layer which is disposed between the lower membrane sheet and the upper membrane sheet, forms a switching hole corresponding to the lower electrode and the upper electrode, and makes the lower electrode and the upper electrode spaced apart from each other by way of the switching hole, wherein the key switch performs a switching operation such that by pushing down the key top against a biasing force of the spring member, the upper electrode and the lower electrode are brought into contact with each other by way of the pushdown projection through the opening, and a spring sheet formed of a thin metal plate is arranged over the upper membrane sheet.
With respect to the above-mentioned key switch, by pushing down the key top against the biasing force of the spring member, the upper electrode of the upper membrane sheet and the lower electrode of the lower membrane sheet are brought into contact with each other by way of the pushdown projection through the opening member so as to perform the switching operation. Since the spring sheet made of metal thin plate is arranged over the upper membrane sheet in performing such a switching operation, even when a state in which goods are placed on the key top is held for a long period, the upper membrane sheet is not plastically deformed due to the large resilient force of the spring sheet whereby the elastic restoring force is maintained over a long period thus ensuring the reliable switching operation.
Further, according to another aspect of the present invention, there is provided a personal computer which comprises a key board which inputs various data such as characters, symbols or the like, the keyboard including key switches each of which comprises a key top which forms a pushdown projection on a lower surface thereof, a holder member which is arranged below the key top and forms an opening therein corresponding to the pushdown projection, a first link member and a second link member which are movably engaged and connected to a lower surface of the key top and the holder member and guide the vertical movement of the key top, a spring member which biases the key top upwardly, and a membrane switch which includes a lower membrane sheet which is arranged below the holder member and forms a lower electrode on an upper surface thereof corresponding to the opening, an upper membrane sheet which forms an upper electrode on a lower surface thereof corresponding to the lower electrode, and a spacer layer which is disposed between the lower membrane sheet and the upper membrane sheet, forms a switching hole corresponding to the lower electrode and the upper electrode, and makes the lower electrode and the upper electrode spaced apart from each other by way of the switching hole, wherein the key switch performs a switching operation such that by pushing down the key top against a biasing force of the spring member, the upper electrode and the lower electrode are brought into contact with each other by way of the pushdown projection through the opening, and the key switch includes a spring sheet made of a thin metal plate which is arranged over the upper membrane sheet; display means which displays characters and symbols or the like; and control means which makes the display means display the characters, symbols or the like based on input data from the keyboard.
In the above-mentioned personal computer, when various data such as characters, symbols or the like are inputted from the key switch of the keyboard, the characters, the symbols and the like are displayed by display means through the control by the control means. Here, the personal computer is provided with the keyboard which is attached with the above-mentioned key switch, an advantageous effect similar to that of the above-mentioned case can be obtained.
(2) Further, in the above-mentioned membrane switch, it is preferable that a semispherical bulging portion is formed in the spring sheet corresponding to the upper electrode. In such a membrane switch, the spring sheet formed of a thin metal plate is arranged over the upper membrane sheet. Since the semispherical bulging portion is formed on the spring sheet corresponding to the upper electrode, when the bulging portion is pushed using a finger, a rubber spring, a key top or the like at the time of performing the switching operation, the upper membrane sheet is pushed by means of a connecting portion with the spring sheet which is present around the bulging portion, and the upper electrode of the upper membrane sheet is brought into contact with the lower electrode of the lower membrane sheet through the switching hole of the spacer layer thus performing the switching operation. Here, the upper membrane sheet is pushed by a connecting portion between the bulging portion and the spring sheet, even when the pushing position of the bulging portion due to a finger, a rubber spring, a key top or the like is disposed at a portion other than a center portion of the bulging portion, it is possible to bring the upper electrode of the upper membrane sheet and the lower electrode of the lower membrane sheet into contact with each other reliably and in a stable manner. Due to such a constitution, it is possible to perform the switching operation in a stable manner.
Further, it is preferable that a pair of slits are formed at both sides of the bulging portion in the above-mentioned spring sheet. In such a membrane switch, since a pair of slits are formed at both sides of the bulging portion formed on the spring sheet, even when a pushdown load is applied to the bulging portion of the spring sheet corresponding to the upper electrode by way of a finger, a rubber spring, a key top or the like, it is possible to concentrate the pushdown load to a connecting portion between the bulging portion and the spring sheet by preventing the pushdown load from being dispersed over the whole spring sheet. Accordingly, it is possible to perform the switching operation rapidly by bringing the upper electrode of the upper membrane sheet and the lower electrode of the lower membrane sheet into contact with each other with a small pushdown load.
Further, it is preferable that a pair of resilient cut-and raised lugs are formed in the spring sheet corresponding to the upper electrode. In such a membrane switch, a spring sheet formed of a thin metal plate is arranged over the upper membrane sheet and a pair of resilient cut-and-raised lugs are formed in the spring sheet corresponding to the upper electrode and hence, when respective resilient cut-and-raised lugs are pushed by a finger, a rubber spring, a key top or the like at the time of performing the switching operation, the upper membrane sheet is pushed by way of the connecting portion between the resilient cut-and-raised lugs and spring sheet, and the upper electrode of the upper membrane sheet is brought into contact with the lower electrode of the lower membrane sheet through the switching hole of the spacer layer thus performing the switching operation. Here, since the upper membrane sheet is pushed by the connection portions formed between respective resilient cut-and-raised lugs and the spring sheet, even when both of the resilient cut-and-raised lugs are simultaneously pushed or when only one resilient cut-and-raised lug is pushed by a finger, a rubber spring, a key top or the like, it is possible to bring the upper electrode of the upper membrane sheet and the lower electrode of the lower membrane sheet into contact with each other surely and in a stable manner. Accordingly, the switching operation can be performed in a stable manner.
Here, it is preferable that a pair of slits are formed in the spring sheet at both sides of the resilient cut-and-raised lugs. In such a membrane switch, since a pair of slits are formed at both sides of the resilient cut-and-raised lugs formed on the spring sheet, even when a pushdown load is applied to the respective resilient cut-and-raised lugs of the spring sheet corresponding to the upper electrode by way of a finger, a rubber spring, a key top or the like, it is possible to concentrate the pushdown load to connecting portions between the resilient cut-and-raised lugs and the spring sheet by preventing the pushdown load from being dispersed over the whole spring sheet. Accordingly, it is possible to perform the switching operation rapidly by bringing the upper electrode of the upper membrane sheet and the lower electrode of the lower membrane sheet into contact with each other with a small pushdown load.
(3) Further, according to another aspect of the present invention, there is provided a membrane switch which comprises a lower membrane sheet which forms a lower electrode on an upper surface thereof, an upper membrane sheet which forms an upper electrode on a lower surface thereof corresponding to the lower electrode, and a spacer layer which is disposed between the lower membrane sheet and the upper membrane sheet, forms a switching hole therein corresponding to the lower electrode and the upper electrode, and makes the lower electrode and the upper electrode spaced apart from each other by way of the switching hole, wherein air grooves are formed in the spacer layer and, at the same time, air bleeding holes are formed in the lower membrane sheet such that the air bleeding holes are positioned inside the air grooves.
In the above-mentioned membrane switch, the air grooves are formed in the spacer layer and, at the same time, the air bleeding holes are formed in the lower membrane sheet such that the air bleeding holes are positioned inside the air grooves. Accordingly, at the time of fixing the lower membrane sheet by adhesion to the support plate or the like using an adhesive agent or a pressure sensitive adhesive double-sided tape, even when bubbles remain between a lower surface of the lower membrane sheet and an adhesive surface of the support plate, it is possible to leak such bubbles to the air grooves through the air bleeding holes. Accordingly, it is possible to surely fix the membrane sheet by adhesion to an adhesive surface of the support plate always in a flat state.
Here, the spacer layer may be formed between the upper membrane sheet and the lower membrane sheet and may be constituted of an adhesive agent layer which adheres both membrane sheets in a laminated manner. In such a case, the air grooves are formed in the adhesive agent layers. Further, the spacer layer may be constituted of a spacer sheet which is formed of a sheet used for forming the upper membrane sheet or the lower membrane sheet. In such a case, the air grooves are formed in the adhesive agent layer which is formed on the spacer sheet by coating.
Further, it is preferable that the air grooves formed in the spacer layer are communicated with the outside of the membrane switch. In such a case, bubbles which remain between a lower surface of the lower membrane sheet and an adhesive surface of the support plate leaks to the outside of the membrane switch through the air bleeding holes and the air grooves. Here, the air grooves formed in the spacer layer do not cause any problems even when the air grooves are not communicated with the outside of the membrane switch. In such a case, the bubbles which pass the air bleeding holes of the lower membrane sheet dwell in the inside of the air grooves and are alleviated by the whole air grooves.
Further, it is preferable that the air grooves are communicated with the outside and the switching hole and, at the same time, the air grooves are formed in a plural number using the switching hole as a start point, and the air bleeding holes are continuously formed in a plural number in and along respective air grooves. In such a membrane switch, the air grooves which are communicated to the outside as well as to the switching hole are formed in a plural number using the switching hole as a start point and, at the same time, the air bleeding holes are continuously formed in a plural number along respective air grooves. Accordingly, at the time of fixing the lower membrane sheet of the membrane switch by adhesion to a support plate or the like using an adhesive agent or a pressure sensitive adhesive double-sided tape, even when bubbles remain between a lower surface of the lower membrane sheet and an adhesive surface of the support plate in a broad range, it is possible to leak such bubbles to the outside through the air bleeding holes and the air grooves. Further, in performing the switching operation by pushing an upper surface of the upper electrode of the upper membrane sheet, it is possible to leak air in the inside of the switching hole to the outside through the air grooves and hence, it is possible to always perform the switching operation in a stable manner.
Further, it is preferable that the switching hole is formed larger than the lower electrode and at least one of a plurality of air bleeding holes is arranged in the inside of the switching hole. In such a membrane switch, the switching hole is formed larger than the lower electrode and at least one of a plurality of air bleeding holes is arranged in the inside of the switching hole and hence, at the time of fixing the lower membrane sheet of the membrane switch by adhesion to the support plate or the like using an adhesive agent or a pressure sensitive adhesive double-sided tape, even when bubbles remain in a portion which corresponds to the switching hole between a lower surface of the lower membrane sheet and an adhesive surface of the support plate, such bubbles can be rapidly and surely leaked to the outside through the air bleeding hole which is arranged in the inside of the switching hole, the switching hole and the air grooves.
Further, according to another aspect of the present invention, there is provided a key switch which comprise a key top which forms a pushdown projection on a lower surface thereof, a holder member which is arranged below the key top and forms an opening therein corresponding to the pushdown projection, a first link member and a second link member which are movably engaged with and connected to a lower surface of the key top and the holder member and guide the vertical movement of the key top, a spring member which biases the key top upwardly, and a membrane switch including a lower membrane sheet which is arranged below the holder member and forms a lower electrode on an upper surface thereof corresponding to the opening, an upper membrane sheet which forms an upper electrode on a lower surface thereof corresponding to the lower electrode, and a spacer layer which is disposed between the lower membrane sheet and the upper membrane sheet, forms a switching hole corresponding to the lower electrode and the upper electrode, and makes the lower electrode and the upper electrode spaced apart from each other by way of the switching hole, wherein the key switch performs a switching operation such that by pushing down the key top against a biasing force of the spring member, the upper electrode and the lower electrode are brought into contact with each other by way of the pushdown projection through the opening, and air grooves are formed in the spacer layer, and air bleeding holes are formed in the lower membrane sheet such that the air bleeding holes are arranged in the inside of the air grooves.
In the above-mentioned key switch, the previously-mentioned membrane switch is used as the membrane switch arranged below the holder member. Accordingly, in the same manner as the above-mentioned case, the air grooves are formed in the spacer layer and, at the same time, the air bleeding holes are formed in the lower membrane sheet such that the air bleeding holes are positioned inside the air grooves. Accordingly, at the time of fixing the lower membrane sheet of the membrane switch by adhesion to the support plate or the like using an adhesive agent or a pressure sensitive adhesive double-sided tape, even when bubbles remain between a lower surface of the lower membrane sheet and an adhesive surface of the support plate, it is possible to leak such bubbles to the air grooves through the air bleeding holes. Accordingly, it is possible to surely fix the membrane sheet by adhesion to an adhesive surface of the support plate always in a flat state.
Further, according to another aspect of the present invention, there is provided a personal computer which comprises a keyboard which inputs various data such as characters, symbols or the like, the keyboard including key switches each of which comprises a key top which forms a pushdown projection on a lower surface thereof, a holder member which is arranged below the key top and forms an opening therein corresponding to the pushdown projection, a first link member and a second link member which are movably engaged with and connected to a lower surface of the key top and the holder member and guide the vertical movement of the key top, a spring member which biases the key top upwardly, and a membrane switch including a lower membrane sheet which is arranged below the holder member and forms a lower electrode on an upper surface thereof corresponding to the opening, an upper membrane sheet which forms an upper electrode on a lower surface thereof corresponding to the lower electrode, and a spacer layer which is disposed between the lower membrane sheet and the upper membrane sheet, forms a switching hole corresponding to the lower electrode and the upper electrode, and makes the lower electrode and the upper electrode spaced apart from each other by way of the switching hole, wherein the key switch performs a switching operation such that by pushing down the key top against a biasing force of the spring member, the upper electrode and the lower electrode are brought into contact with each other by way of the pushdown projection through the opening, and air grooves are formed in the spacer layer and air bleeding holes are formed in the lower membrane sheet such that the air bleeding holes are positioned in the inside of the air grooves; display means which displays characters and symbols or the like; and control means which makes the display means display the characters, symbols or the like based on input data from the keyboard.
In the above-mentioned personal computer, when various data such as characters, symbols or the like are inputted from the key switch of the keyboard, the symbols and the like are displayed by display means through the control by the control means. Here, the personal computer is provided with the keyboard which is attached with the above-mentioned key switch, advantageous effect similar to that of the above-mentioned case can be obtained.
(4) Further, according to an other aspect of the present invention, there is provided a key switch which comprises a key top which forms a plurality of slide engaging portions on a lower surface thereof, a holder member which is arranged below the key top and forms a plurality of rotary engaging portions thereon, first and second link members which are engaged with the slide engaging portions of the key top and the rotary engaging portions of the holder member respectively, cross each other in an X shape as viewed from a side, and guides a vertical movement of the key top, a switching portion which performs a switching operation based on a pushdown operation of the key top, and a spring member which is formed of a thin resilient metal plate, biases the key top upwardly, and includes a pushing portion which performs the switching operation by acting on the switch portion at the time of pushing down the key top at a center portion thereof, wherein at least pushing portion of the spring member and a peripheral portion thereof are arranged in a concave shape as viewed from a side, and deformation action portions which deform the spring member in a U-shape at the time of pushing down the key top are provided to portions of the first link member and the second link member at sides thereof disposed closer to the rotary engaging portion sides than a crossing portion of both link members as viewed from a side.
In the above-mentioned key switch, with respect to the spring member which biases the key top upwardly and is formed of the thin resilient metal plate, at least the pushing portion and the peripheral portion thereof are arranged in a concave shape as viewed from a side and hence, it is possible to ensure the deformation direction of the spring member. Further, with respect to the first link member and the second link member, since the deformation action portions are provided to the portions closer to the rotary engaging portions of the holder member than the crossing portion of both link members as viewed from a side, at the time of pushing down the key top, the spring member is deformed in a U-shape due to the deformation action portions of the link members and, at the same time, the pushing portion of the spring member is lowered thus enabling the reliable switching operation. Further, since the spring member is formed of the thin resilient metal plate and hence, it is possible to ensure the stable characteristics such as key operability without receiving the influence of the use environment due to the high durability held by the thin resilient metal plate.
Here, in the above-mentioned key switch, it is preferable that a first holding portion is formed on the first link member and a second holding portion is formed on the second link member, and the spring member is extended between the first holding portion and the second holding portion so as to form the deformation action portions. In such a key switch, since the first holding portion and the second holding portion which are served for extending the spring member are also commonly used as the deformation action portions which deform the spring member, it is not necessary to especially provide the deformation action portions of the spring member so that the constitution of the first link member and the second link member can be simplified.
Further, it is preferable that a first holding hole into which the first holding portion is loosely fitted and a second holding hole into which the second holding portion is loosely fitted are formed in the spring member, and the spring member is formed such that a width thereof is gradually increased toward a center portion thereof from the first holding hole and the second holding hole. In such a key switch, since the width of the spring member is increased toward the center portion thereof from the first holding hole and the second holding hole, a stress generated in the spring member due to the pushdown operation of the key top is dispersed at the center portion having the large width and hence, the concentration of the pushdown stress in the center portion can be surely prevented. Accordingly, the durability of the spring member can be enhanced.
Further, it is preferable that the above-mentioned spring member is formed in an approximately circular shape in a plan view. In such a key switch, since the spring member is formed in an approximately circular shape in a plan view, it is possible to uniformly disperse the stress which is generated in the spring member due to the pushdown operation of the key top over the whole spring member. Accordingly, the durability of the spring member can be further remarkably enhanced.
Further, it is preferable that the switching portion is constituted of a membrane switch which is arranged below the holder member and the spring member is curved downwardly along with the pushdown operation of the key top so as to operate the membrane switch. In such a key switch, the membrane switch is operated by way of the spring member which is curved downwardly along with the pushdown operation of the key top and hence, it is totally unnecessary to form a pushdown projection for pushing the membrane switch to the key top whereby the reduction of the thickness of the key switch can be easily achieved.
Further, according to another aspect of the present invention, there is provided a personal computer which comprises: a keyboard which inputs various data such as characters, symbols or the like, the keyboard including key switches each of which comprises a key top which forms a plurality of slide engaging portions on a lower surface thereof, a holder member which is arranged below the key top and forms a plurality of rotary engaging portions thereon, first and second link members which are engaged with the slide engaging portions of the key top and the rotary engaging portions of the holder member respectively, cross each other in an X shape as viewed from a side, and guide a vertical movement of the key top, a switching portion which performs a switching operation based on a pushdown operation of the key top, and a spring member which is formed of a thin resilient metal plate, biases the key top upwardly, and includes a pushing portion which performs the switching operation by acting on the switch portion at the time of pushing down the key top at a center thereof, wherein at least the pushing portion of the spring member and a peripheral portion thereof are arranged in a concave shape as viewed from a side, and deformation action portions which deform the spring member in a U-shape at the time of pushing down the key top are provided to portions of the first link member and the second link member at sides thereof disposed closer to the rotary engaging portion sides than a crossing portion of both link members as viewed from a side; display means which displays characters and symbols or the like; and control means which makes the display means display the characters, symbols or the like based on input data from the keyboard.
In the above-mentioned personal computer, when various data such as characters, symbols or the like are inputted from the key switch of the keyboard, the characters, the symbols and the like are displayed by display means through the control by the control means. Here, the personal computer is provided with the keyboard which is attached with the above-mentioned key switches, an advantageous effect similar to that of the above-mentioned case can be obtained.